<!-- Include Jquery--->
<script type="text/javascript" src="jquery-1.7.2.min.js"></script>

<script type="text/javascript">

  $(document).ready(function(){

     $('.txt').click( function (){
       var divHtml = $('#mainDiv').html();
       alert (divHtml);
     });


  });
</script>


<input class="txt" type="button" value="Click Here to get the value of below paragraph">


<div id="mainDiv">
  Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s
</div>
